The history and significance of beards goes back a long, long way. Beards means a great deal to most individuals, many cultures and religions. Some like them long, others short and some none at all.
Have you ever thought that some beards could be an indicator of the quality of air in a place? Better still; some beards also can help you locate the true north?
It is not human beards! It is the Usnea lichens better known as Old Man’s Beard or Methuselah Beards.
Usnea, pronounced ooze-nee-ah is the elastic, yellow greenish lichen that grows from tree trunks and branches in forests. They usually grow on old or dead deciduous and conifers trees in a moist forest.
It is considered as the best natural bio indicator of level of pollution in an area. Where the air is unpolluted, they can grow up to 2 feet long! Where the air is polluted, they rarely grow. They grow only in areas where the air is clean and of high quality. They are very sensitive to air pollution especially sulfur dioxide and acidic rain.
That is why you will rarely find them on roadsides but in plenty in some forests. In your endevours, if you come across the old man’s beard, be sure you are in a relatively clean and healthy environment. However, lack of Usnea in a region does not necessarily mean the area is polluted. It may be because the habitat is too dry and sunny, since the lichen need some moist and shade to thrive.
How can you distinguish Usnea from other lichen? They are elastic while other lichens are not. Hold a strand of the lichen in your fingers and gently pull on both ends. The outer green yellowish sheath will split, revealing white inner pith that will stretch before breaking.
There is an old adage that ‘moss grows on the north side of the trees’. The old man’s beard may sometimes help you to locate the true north but will also equally deceive you if you are not keen.
Usnea grows on the moist sides of trees, given that its primary source of moisture is from the air. In open forests, the moist side is most likely to be the shaded, north side. But in closed-canopy forests that hold moisture well, Usnea may grow on all sides of the trees. Several factors come into play. Key determinant is why is that part of the tree moist? Is the bark rough? Is the gradient shallow that rain water run slowly? Is the area direct near a water sources? Is the water dripping from overhanging branches?
If you find a nearly vertical smooth surface that is not too close to water source and has old man’s beard, the only reason for the side staying moist is it is in shade in the middle of the day.
Hanging down from trunks and branches, Usnea resembles an upside-down version of underwater coral, another vulnerable barometer of pollution worldwide.
Next time you find yourself in the national park or a forest, keep an eye out for Usnea. As long as it is growing and healthy, take a deep breath and enjoy the high quality air.
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